Aircraft fuselage cells for large aircraft are at the present time predominantly formed with monolithic skin fields. For purposes of stiffening a multiplicity of longitudinal stiffeners, running parallel to the flight direction and separated from one another, are provided on the inner faces of the monolithic skin fields. Moreover a multiplicity of annular frames are arranged on the inner faces of the skin fields, in each case aligned transversely to the flight direction. The monolithic skin fields, thus reinforced, are in the manner of multi-shell construction completed to form barrel-like fuselage sections and are then joined in series one behind another to form a complete aircraft fuselage cell.
Furthermore double-shell skin fields for the manufacture of fuselage cell structures are of known art in which a core structure is provided on both faces with an inner and an outer covering layer to create a sandwich-type structure curved in at least one dimension. The core structure used can be of any form of spatial embodiment, for example a honeycomb core, a foam core or a folded comb core, to provide a preferably uniform separation distance between the covering layers.
The double-shell skin fields have the advantage, amongst others, that a significantly reduced number of longitudinal stiffeners and annular frames are required for reinforcement, resulting in a reduction of manufacturing resource and weight. In the ideal case the frames and longitudinal stiffeners can be dispensed with entirely. Moreover a double-shell skin field features excellent thermal insulation properties, such that the additional primary thermal insulation with insulation material that is otherwise required in the case of monolithic skin fields can at least partially be dispensed with. Furthermore it is of known art to form fuselage cell structures with fuselage sections that are manufactured with a combination of monolithic and double-shell skin fields so as to combine the specific advantages of these forms of construction.
Irrespective of the use of monolithic skin fields and/or double-shell skin fields in the manufacture of a fuselage section it is generally essential for psychological reasons to integrate a multiplicity of windows into the fuselage cell structure, at least in the case of passenger aircraft. However, from the structural viewpoint the windows represent a significant weakening of the primary structure and require in general an increase in the weight. Accordingly, from the prior art a multiplicity of weight-optimised solutions for the installation of windows in aircraft fuselage cells are of known art.
From DE 10 2005 058 749 A1 for example a solution optimised in terms of weight and strength using a surrounding contact pressure frame for the integration of a window into a monolithic skin field is of known art.